When sharing system audio on Windows while sharing a screen, you may also be sharing audio from remote participants and cause echo. To prevent echo, you can enable the echo canceller via the MediaTrackConstraints in ScreenShareOptions. The downside of enabling the echo canceller on any platform is that the sent audio may sound distorted. Hence, if preserving the quality of the sent audio is important for you, leave the echo canceller disabled and mitigate the occurrence of echo by muting remote participants.
Updated 8 months ago